Inverter AC Bus Bar Assembly

ABSTRACT

Power inverter assemblies are provided herein for use with motor vehicles. An inverter assembly may have a symmetrical structure configured to convert DC input power to AC output power. The inverter assembly may include a housing enclosing a symmetrical DC input portion, a symmetrical AC output portion, a DC link capacitor, and a gate drive portion having a pair of power modules. The symmetrical DC input portion can include a DC input bus bar sub-assembly to which the DC link capacitor is coupled, and a second DC bus bar sub-assembly that may electrically couple the DC link capacitor with the power modules. The symmetrical AC output portion may include a three phase output AC bus bar sub-assembly to which the power modules can be electrically coupled. A cooling sub-assembly may be provided for cooling the power modules with fluid transfer using a coolant.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to U.S. patent application Ser. No. ______, filed Aug. 31, 2015, titled “Inverter Assembly,” and U.S. patent application Ser. No. ______, filed Aug. 31, 2015, titled “Inverter DC Bus Bar Assembly,” both of which are herein incorporated by reference in their entirety.

FIELD OF THE PRESENT DISCLOSURE

The present disclosure relates generally to an inverter assembly and, more specifically, but not by limitation, to an inverter assembly comprising structures configured to convert a DC input to a three phase AC output.

SUMMARY OF THE PRESENT DISCLOSURE

According to various embodiments, the present disclosure may be directed to a three phase output AC bus bar sub-assembly for an inverter assembly, the three phase output AC bus bar sub-assembly comprising: (a) three bus bars each comprising: (i) a bar body having a front surface and a back surface; (ii) a plurality of power module tabs spaced apart from one another so as to allow a first of the plurality of power module tabs to couple with a first power module of the inverter assembly and a second of the plurality of power module tabs to couple with a second power module of the inverter assembly, the plurality of power module tabs extending away from the back surface; and (iii) an output tab extending from the front surface; and (b) the bar body of a first of the three bus bars is positioned behind the bar body of a second of the three bus bars and a third of the three bus bars is positioned in front of the second of the three bus bars.

According to some embodiments, the present disclosure may be directed to a three phase output AC bus bar sub-assembly for an inverter assembly, the three phase output AC bus bar sub-assembly comprising: (a) three bus bars each comprising: (i) a bar body having a front surface and a back surface, wherein the front surface and the back surface both comprise an insulating coating; (ii) a plurality of power module tabs spaced apart from one another so as to allow a first of the plurality of power module tabs to couple with a first power module of the inverter assembly and a second of the plurality of power module tabs to couple with a second power module of the inverter assembly, the plurality of power module tabs extending away from the back surface; and (iii) an output tab extending from the front surface; and (b) the bar body of a first of the three bus bars is positioned behind the bar body of a second of the three bus bars and a third of the three bus bars is positioned in front of the second of the three bus bars.

According to some embodiments, the present disclosure may be directed to a three phase output AC bus bar sub-assembly, comprising: (a) an offset arrangement of three bus bars, the three bus bars each comprising: (i) a pair of power module tabs extending perpendicularly from a bar body, the pair of power module tabs disposed on opposing sides of the bar body; and (ii) an output bar extending perpendicularly from the bar body in a direction that is opposite of a direction of the pair of power module tabs, wherein the output bar is disposed between the pair of power module tabs; and (b) a mounting plate that receives the output bars of the three bus bars; and (c) wherein the pair of power module tabs of the three bus bars extend in linear alignment with one another along a line of symmetry.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the present disclosure are illustrated by the accompanying figures. It will be understood that the figures are not necessarily to scale and that details not necessary for an understanding of the technology or that render other details difficult to perceive may be omitted. It will be understood that the technology is not necessarily limited to the particular embodiments illustrated herein.

FIG. 1 is a perspective view of an exemplary drive train that can comprise inverter assemblies of the present disclosure.

FIG. 2 is a perspective view of an exemplary inverter assembly.

FIG. 3 is an exploded perspective view of the exemplary inverter assembly of FIG. 2.

FIG. 4 is a top down view of the exemplary inverter assembly with a top cover removed.

FIGS. 5A, 5B, and 5C are various views of an exemplary DC bus bar sub-assembly.

FIG. 6 is a perspective view of a portion of another exemplary DC bus bar sub-assembly.

FIG. 7 is a perspective view of the exemplary DC bus bar sub-assembly connected to power cables.

FIG. 8 is a top elevation view that illustrates an exemplary DC link capacitor of the inverter assembly, where the DC link capacitor may comprise a capacitor bank.

FIG. 9A is a perspective view of an exemplary DC input bus bar that couples the DC link capacitor with power modules.

FIG. 9B is an exploded perspective view of another exemplary DC input bus bar of FIG. 9A.

FIG. 9C is a cross sectional view of the exemplary DC input bus bar of FIGS. 9A and 9B.

FIG. 10 is a perspective view of the exemplary DC input bus bar installed into the inverter assembly.

FIG. 11 is a partial exploded perspective view of exemplary power modules.

FIG. 12 is a perspective view of an exemplary three phase output AC bus bar sub-assembly.

FIG. 13 is another perspective view of the exemplary three phase output AC bus bar sub-assembly.

FIG. 14 is a perspective view of the exemplary three bus bars of the three phase output AC bus bar sub-assembly.

FIG. 15 is a top down view of the exemplary three phase output AC bus bar sub-assembly installed into the inverter assembly.

FIG. 16 is a perspective view of the exemplary three phase output AC bus bar sub-assembly coupled with power cables.

FIG. 17 is an exploded view of an exemplary cooling assembly.

FIGS. 18A-C illustrate an exemplary alternative cooling assembly.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

While this technology is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail several specific embodiments with the understanding that the present disclosure is to be considered as an exemplification of the principles of the technology and is not intended to limit the technology to the embodiments illustrated.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It will be understood that like or analogous elements and/or components, referred to herein, may be identified throughout the drawings with like reference characters. It will be further understood that several of the figures are merely schematic representations of the present disclosure. As such, some of the components may have been distorted from their actual scale for pictorial clarity.

In general, the present disclosure is directed to inverter assemblies and their methods of manufacture and use. An example inverter assembly can comprise a symmetrical structure configured to convert DC input power to AC output power.

Some embodiments can include a symmetrical DC input section, a symmetrical AC output section, a gate drive circuit board, and a controller. The gate drive circuit board and controller can be associated with two inverter power modules coupled in parallel. The power modules can provide currents significantly exceeding 400 amps RMS (root mean squared) and in various embodiments, each can comprise an IGBT (insulated gate bipolar transistor), or other suitable element, for switching the direct current into an alternating current. The total RMS current may exceed that which may be typically available by a single commercially available power module. The DC input section can include a DC input bus and a DC bus sub-assembly. The DC bus sub-assembly can have a symmetrical structure with a layered design, including a positive plate and a negative plate substantially overlapping each other. The positive plate can be coupled to the positive terminal of the DC input bus through a plurality of positive input tabs. The negative plate can be coupled to the negative terminal of the DC input bus through a plurality of negative input tabs. The positive plate can have two or more positive output tabs and two or more negative output tabs coupled to the input terminals of the two inverter power modules.

The AC output section can include a plurality of output bus bars, each having a symmetrical structure. In an embodiment, the AC output section can provide a three-phase AC power signal. Each of the output bus bars can correspond to a channel (phase) of the three-phase AC power signal. Each bus bar can include two input tabs coupled to output terminals of each channel of the two inverter power modules and an output tab coupled to an AC output terminal of the inverter. The output tab may be disposed at substantial equal distances from the two input tabs of each AC bus bar. These and other advantages of the present disclosure will be described in greater detail infra with reference to the collective drawings.

Referring now to FIG. 1, which illustrates the positioning of two inverter assemblies, such as exemplary inverter assembly 102. The inverter assemblies can be disposed on an exemplary drive train 104.

FIGS. 2 and 3 collectively illustrate the exemplary inverter assembly 102 which can comprise a housing 106 that can comprise a lower enclosure 108 and a cover 110.

FIG. 4 is a top down view of the exemplary inverter assembly 102 with the cover 110 removed to expose internal components of the inverter assembly 102. In some embodiments, the inverter assembly 102 can comprise a DC bus sub-assembly (referred to herein as “DC bus bar 112”), a DC link capacitor 114 (which may comprise a capacitor bank and also be referred to as DC link capacitor bank 114), a DC input bus bar sub-assembly 170, a gate drive circuit board 116, and a three phase output AC bus bar sub-assembly 118.

FIGS. 5A-C collectively illustrate the example DC bus bar 112 that can comprise a pair of bus bars, namely a positive bus bar 120 and a negative bus bar 122. Each of the bus bars can comprise an input tab and an output tab. For example, positive bus bar 120 may comprise a positive input tab 124 and a positive output tab 126, while negative bus bar 122 may comprise a negative input tab 128 and a negative output tab 130.

Both the positive bus bar 120 and the negative bus bar 122 can have a bar body that spans between their respective input tab and output tab. In one embodiment, the positive bus bar 120 can have a positive bar body 132 and the negative bus bar can comprise a negative bar body 134.

In some embodiments, the positive bus bar 120 and the negative bus bar 122 can be shaped similarly to one another. Both the positive bus bar 120 and negative bus bar 122 can have a first section and a second section. For example, the positive bus bar 120 can have a first section 136 and a second section 138. In some embodiments, the first section 136 and the second section 138 can be positioned relative to one another at a substantially right angle configuration. That is, the first section 136 may extend perpendicularly from the second section 138.

The negative bus bar 122 can comprise a first section 140 and a second section 142. In some embodiments, the first section 140 and second section 142 can be positioned relative to one another at a substantially right angle.

The input tabs on both the positive bus bar 120 and the negative bus bar 122 extend from their respective bar body. For example, the positive input tab 124 can extend in linear alignment with the first section 136 of the positive bar body 132. The positive output tab 126 can extend rearwardly from the second section 138 of the positive bus bar 120.

The positive bus bar 120 and the negative bus bar 122 can be placed into mating relationship with one another such that the positive bus bar 120 may be nested within the negative bus bar 122 with both being electrically isolated from one another. A space can exist between the positive bar body 132 and the negative bar body 134. The size of this space can be minimized, which can reduce inductance through the DC bus bar 112 and can minimize noise pick-up from stray fields within the inverter enclosure.

In one embodiment, the negative output tab 130 of the negative bus bar 122 may be offset to a side of the second section 142 of the negative bar body 134. Conversely, the positive output tab 126 of the positive bus bar 120 may be offset to a side of the second section 138 of the positive bar body 132. In one embodiment, the negative output tab 130 and the positive output tab 126 can be spaced apart from one another due to their positioning on their respective sides of their associated bar body. Similarly, the positive input tab 124 and the negative input tab 128 can be spaced apart from one another and can be individually secured to a terminal block, which is described in greater detail below.

In some embodiments, the space between the positive bar body 132 and the negative bar body 134 can be filled with an electrical insulator such as a Mylar™ film. Likewise, surfaces of the positive bar body 132 and the negative bar body 134 that face one another can be coated with a layer of an electrically insulating material rather than disposing an electrically insulating layer therebetween.

In some embodiments, the first section 136 of positive bar body 132 and the first section 140 of the negative bar body 134 can be surrounded, at least partially, with an input core 149. The input core 149 may be configured to contact a terminal block 146 onto which the pair of bus bars can be installed.

For example, the terminal block 146 can provide a mounting surface that supports the DC bus bar 112. The terminal block 146 can mount to the inner sidewall of the lower enclosure 108 and a lower support 148 of the lower enclosure 108.

In some embodiments, the input core 149 may be secured to the terminal block 146 using a compression plate 150. A spacer 152 can be disposed between the input core 149 and the compression plate 150. In one embodiment, the spacer 152 may be a silicon foam block, although other materials that would be known to one of ordinary skill in the art can also likewise be utilized in accordance with the present disclosure.

Another example of a DC bus bar 112 is illustrated in FIG. 6. In this embodiment, the input tabs 141 and 143 can angle upwardly and outwardly from the bar bodies along reference line A, rather than in linear alignment. Also, the input tabs 141 and 143 can extend from a side edge of the bar bodies, while output tabs 145 and 147 can extend in alignment with reference line B. To be sure, reference line A and reference line B can be substantially perpendicular to one another.

Turning to FIG. 7, the positive input tab 124 and negative input tab 128 can be illustrated as being coupled with input power cables 158 and 160, respectively.

FIG. 8 is a top elevation view that illustrates the exemplary DC link capacitor 114 of the inverter assembly, where the DC link capacitor may comprise a capacitor bank. As illustrated in FIG. 8, in some embodiments, the DC bus bar 112 may be electrically coupled to the DC link capacitor 114 through a first connector 154 and a second connector 156. (The first connector and second connector 156 may variously be positive and negative connectors depending on the arrangement of the polarities provided by the DC bus bar 112.) According to some embodiments, the first connector 154 and second connector 156 can be coupled or embedded within the DC link capacitor 114. To be sure, the DC link capacitor 114 can be potted into place within the lower enclosure 108; the first connector 154 and second connector 156 being embedded into the DC link capacitor 114 during the potting process.

Additionally, a positive output bus bar 162 may be embedded into the DC link capacitor 114, along with a negative output bus bar 164. Both the positive output bus bar 162 and the negative output bus bar 164 comprise a plurality of output tabs. For example, the positive output bus bar 162 can comprise positive output tabs 166A-C, while negative output bus bar 164 can comprise negative output tabs 168A-C. In some embodiments, the positive output tabs 166A-C and the negative output tabs 168A-C can be positioned in linear alignment with one another. The positive output tabs 166A-C and the negative output tabs 168A-C can also be alternatingly positioned such that negative output tab 168A may be positioned between positive output tab 166A and positive output tab 166B, just as an example.

The DC link capacitor 114 can be potted into a void 169, in some instances. In one embodiment, the DC link capacitor 114 is secured within the void 169 with a potting material that can include a mixture of polyol and isocyanate. The potting material can include 100 parts polyol to 20 parts isocyanate, in some embodiments. The DC link capacitor material may be poured into the void 169 to a height of 45 to 50 mm below an upper edge of the void 169. The DC link capacitor material can be cured at 25 degrees centigrade for 24 hours, at 60 degrees centigrade for two hours, or also at 100 degrees centigrade for 20-30 minutes, in various embodiments.

Referring now to FIGS. 9A-10, which illustrate an example DC input bus bar sub-assembly 170. The DC input bus bar sub-assembly 170 can also be referred to as a “second DC bus bar sub-assembly” or “DC input bus bar 170”. The DC input bus bar 170 can comprise a positive bus bar 174 and a negative bus bar 176, which can be arranged into a mating relationship with one another similarly to the DC bus bar 112 described above.

The positive bus bar 174 can comprise a plurality of positive input tabs 178A-C and the negative bus bar 176 can comprise a plurality of negative input tabs 180A-C. When installed, the positive bus bar 174 can couple with the positive output bus bar 162 of the DC link capacitor 114 by connecting the plurality of positive input tabs 178A-C of the positive bus bar 174 with the positive output tabs 166A-C of the positive output bus bar 162 of the DC link capacitor 114. Likewise, the negative bus bar 176 can couple with the negative output bus bar 164 of the DC link capacitor 114 by connecting the plurality of negative input tabs 180A-C of the negative bus bar 176 with the negative output tabs 168A-C of the negative output bus bar 164 of the DC link capacitor 114.

The plurality of positive input tabs 178A-C and the plurality of negative input tabs 180A-C can be arranged in an alternating and linear configuration.

The positive bus bar 174 and negative bus bar 176 can be placed in an overlaid mating relationship with one another. A space 175 may be provided between the positive bus bar 174 and negative bus bar 176, which can be filled with an electrically insulating material, in some embodiments. The space 175 between the positive bus bar 174 and negative bus bar 176 can allow for low inductance of current through the DC input bus bar sub-assembly 170.

The positive bus bar 174 can comprise a pair of positive output tabs 182A and 182B, while the negative bus bar 176 can comprise a pair of negative output tabs 184A (shown in FIGS. 10) and 184B. The pair of positive output tabs 182A and 182B can be disposed on opposing sides of the positive bus bar 174 relative to one another. The pair of negative output tabs 184A and 184B can also be disposed on opposing sides of the negative bus bar 176 relative to one another. The pairs of negative and positive output tabs can be arranged such that positive output tab 182A may be placed in proximity to negative output tab 184A, while positive output tab 182B may be placed in proximity to negative output tab 184B.

As illustrated best in FIG. 10, the DC input bus bar 170 can provide electrical connectivity between the DC link capacitor 114 and the power modules of the gate drive circuit board 116, which will be described in greater detail below. In one embodiment, the positive output tab 182A and negative output tab 184A can be coupled, through an opening in the gate drive circuit board 116, to a first power module 188. The positive output tab 182B and negative output tab 184B can be coupled to a second power module 186.

FIG. 11 is a partial exploded perspective view illustrating exemplary first and second power modules 186 and 188, with the gate drive circuit board removed, as well as the various bus bars and the DC link capacitor described above. Each of the first and second power modules 186 and 188 can comprise a pair of positive and negative input terminals. For example, first power module 186 can include positive terminal 190 and negative terminal 192. Each of the power modules can be coupled to a bottom of the lower enclosure 108 with a gasket, such as gasket 194. In various embodiments, the gaskets can serve to create a fluid impermeable seal that keeps fluid from a cooling sub-assembly from entering the lower enclosure 108. As will be discussed in greater detail herein, heat sinks of the power modules 186 and 188 can be exposed to a coolant fluid by the cooling sub-assembly. The coolant fluid can remove excess heat from the power modules increasing their performance.

Each of the exemplary power modules 186 and 188 can comprise three output terminals that each can output a different phase of an AC power signal that can be generated by the power module. For example, first power module 186 can comprise output terminals 187A, 187B, and 187C and second power module 188 can comprise output terminals 189A, 189B, and 189C.

FIGS. 12 and 13 collectively illustrate an example three phase output AC bus bar sub-assembly (hereinafter “AC bus bar 118”). In some embodiments, the AC bus bar 118 can comprise three bus bars such as a first bus bar 202, a second bus bar 204, and a third bus bar 206.

Each of the first, second and third bus bars 202, 204, 206 can comprise a bar body. For example, first bus bar 202 can comprise a bar body 208, the second bus bar 204 can comprise a bar body 210, and the third bus bar 206 can comprise a bar body 212. Each of the first, second and third bus bars 202, 204, 206 can comprise a front and back surface. For example, the bar body 208 of the first bus bar 202 can comprise a front surface 214 and a back surface 216. The bar body 210 of the second bus bar 204 can comprise a front surface 218 and a back surface 220, while the bar body 212 of the third bus bar 206 can comprise a front surface 222 and a back surface 224.

In one embodiment, the first, second and third bus bars 202, 204, 206 can be spaced apart from one another while being positioned in a nested configuration. Thus, a space 205 can exist between the front surface 214 of the first bus bar 202 and the back surface 216 of the second bus bar 204. Likewise, the third and second bus bars can be spaced apart from one another to form a space 207 between the front surface 214 of the second bus bar 204 and the back surface 220 of the third bus bar 206. The spaces 205 and 207 can each be filled with an electrically insulating material. In other embodiments, the front and/or back surfaces of the bus bars 202, 204, 206 can be coated with an insulating layer of material that can be adapted to provide electrical insulation.

Each of the first, second and third bus bars 202, 204, 206 also can comprise a plurality of power module tabs that can electrically couple each of the bus bars with both the first and second power modules 186 and 188 (see FIG. 11). For example, the first bus bar 202 can comprise power module tabs 226 and 228, while the second bus bar 204 can comprise power module tabs 230 and 232. The third bus bar 206 can comprise power module tabs 234 and 236. The power module tabs of any one of the bus bars can be spaced apart from one another so as to allow for the bus bar to connect with each of the power modules.

The plurality of power module tabs of each of the bus bars can extend away from the back surface of their respective bar body. The plurality of power module tabs 226, 228, 230, 232, 234, and 236, can be coplanar and aligned with one another along a longitudinal axis of alignment Ls (see FIG. 13).

In some embodiments, the first, second and third bus bars 202, 204, 206 can be placed into a nested but offset relationship with one another. For example, second bus bar 204 can be disposed in front of first bus bar 202, while third bus bar 206 can be disposed in front of second bus bar 204. Also, the bus bars can be staggered or offset from one another. The second bus bar 204 can be offset from the first bus bar 202, and the third bus bar 206 can be offset from the second bus bar 204. In this configuration, the power module tab 230 of the second bus bar 204 can be positioned between the power module tab 226 of the first bus bar 202 and the power module tab 234 of the third bus bar 206. Power module tab 234 of the third bus bar can be positioned between the power module tab 230 of the second bus bar 204 and the power module tab 228 of the first bus bar 202. Power module tab 228 of the first bus bar 202 may be positioned between the power module tab 234 of the third bus bar 206 and the power module tab 232 of the second bus bar 204. Power module tab 232 may be positioned between the power module tab 228 of the first bus bar 202 and the power module tab 236 of the third bus bar 206.

In some embodiments, a length of the power module tabs (234, 236) of the third 206 of the three bus bars may be greater than a length of the power module tabs (230, 232) of the second 204 of the three bus bars. Also, the length of the power module tabs (230, 232) of the second 204 of the three bus bars can be greater than a length of the power module tabs (226, 228) of the first 202 of the three bus bars.

Each of the first, second and third bus bars 202, 204, 206 also can comprise an output tab, which can extend from a front surface of their respective bar body. For example, the first bus bar 202 can comprise an output tab 238, the second bus bar 204 can comprise an output tab 240, and the third bus bar 206 can comprise an output tab 242.

In one embodiment, the output tabs 238, 240, and 242 can be arranged so as to be symmetrical in their positioning relative to one another. Due to spacing of the output terminals of each of the power modules (described above), and in order to maintain symmetry of the output tabs 238, 240, and 242, output tab 240 can have a substantially serpentine shaped section 244 that can position the output tab 240 in between output tabs 238 and 242.

In some embodiments, the bus bars 202, 204, 206 can be held in their respective positions using a mounting plate 246 (see FIG. 12). The mounting plate 246 may be adapted with apertures. The output tabs 238, 240, and 242 can each extend through these apertures. In one embodiment, the output tabs 238, 240, and 242 can be secured in place on the mounting plate 246 with locking members, such as locking member 248.

The mounting plate 246 can be coupled to the second and the third of the three bus bars (see example shown in FIG. 12).

Referring now to FIGS. 14 and 15 (and FIGS. 11, 12, and 13), according to some embodiments, power module tabs 226 and 228 of the first bus bar 202 (see FIG. 12) can connect with output terminal 187A (see also FIG. 11) of first power module 186 and output terminal 189A of second power module 188. The second bus bar 204 may connect with output terminal 187B of first power module 186 and output terminal 189B of second power module 188. The third bus bar 206 can couple with output terminal 187C of first power module 186 and output terminal 189C of second power module 188.

In FIG. 16, a plurality of power cables, such as power cable 250 can be coupled with the output tabs 238, 240, and 242 (see FIGS. 14-15) of the AC bus bar 118.

FIG. 17 illustrates an example cooling sub-assembly 252 that can comprise a cooling cavity 254, a gasket 256, cover plate 258, an inlet port 260, an outlet port 262, and a purge port 264. In general, the cooling cavity 254 may be formed by a sidewall 266 formed into a lower enclosure 108 of the housing. Heat sinks 268 and 270 of the power modules 186 and 188, respectively, can be exposed to the cooling cavity 254. As mentioned above, the power modules 186 and 188 can be isolated with gaskets so as to prevent fluid inside the cooling cavity 254 from entering the housing.

When the cover plate 258 may be joined to the lower enclosure 108 of the housing, a fluid, such as a coolant can be pumped into the cooling cavity 254 through the inlet port 260 and can be extracted through the outlet port 262 using a pump (not shown). The purge port 264 can be used to purge trapped air from the cooling cavity 254 if needed.

In one embodiment, the inlet and outlet ports 260 and 262 can be disposed near a center of the housing which can help promote equal flow rate of fluid to each cooling cavity.

FIGS. 18A-C collectively illustrate another embodiment of a cooling sub-assembly. In one embodiment, the first and second power modules 186 and 188 can be mounted to a plate 280. A sidewall (See e.g., 266 in FIG. 17) defines a cooling cavity (See e.g., 254 in FIG. 17). The heat sinks 268 and 270 can be positioned within the cooling cavity 254. An inlet port 286 may be positioned on one end of the cooling cavity 254 and the outlet port 288 may be positioned on the opposing end of the cooling cavity 254. As fluid may be introduced into the inlet port 286 and removed from the outlet port 288, the fluid can remove heat from the first and second power modules 186 and 188 as it communicates over the heat sinks 268 and 270, for providing a substantially equal share of coolant to each power module. In some other embodiments (see e.g., FIG. 17) the inlet port may be positioned substantially midway between heat sinks 268 and 270 such that coolant may be communicated from the substantially midway point so coolant can flow bidirectionally, over the heat sink 268 in one direction and heat sink 270 in the other direction, and be collected substantially in the middle, for providing substantially equal share of coolant to each power module, with less thermal differential across the power modules.

While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. The descriptions are not intended to limit the scope of the technology to the particular forms set forth herein. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments. It should be understood that the above description is illustrative and not restrictive. To the contrary, the present descriptions are intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the technology as defined by the appended claims and otherwise appreciated by one of ordinary skill in the art. The scope of the technology should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents. 

What is claimed is:
 1. A three phase output AC bus bar sub-assembly for an inverter assembly, the three phase output AC bus bar sub-assembly comprising: three bus bars each comprising: a bar body having a front surface and a back surface; a plurality of power module tabs spaced apart from one another so as to allow a first of the plurality of power module tabs to couple with a first power module of the inverter assembly and a second of the plurality of power module tabs to couple with a second power module of the inverter assembly, the plurality of power module tabs extending away from the back surface; and an output tab extending from the front surface; and the bar body of a first of the three bus bars is positioned behind the bar body of a second of the three bus bars and a third of the three bus bars is positioned in front of the second of the three bus bars.
 2. The three phase output AC bus bar sub-assembly according to claim 1, wherein the front surface of one or more of the three bus bars includes an insulating layer.
 3. The three phase output AC bus bar sub-assembly according to claim 1, further comprising an insulating spacer disposed between the front surface of the first of the three bus bars and the back surface of the second of the three bus bars, and another insulating spacer disposed between the front surface of the second of the three bus bars and the back surface of the third of the three bus bars.
 4. The three phase output AC bus bar sub-assembly according to claim 1, further comprising a mounting plate that is coupled to the second and the third of the three bus bars.
 5. The three phase output AC bus bar sub-assembly according to claim 4, wherein the output tab of each of the three bus bars extends through the mounting plate, and wherein the plurality of power module tabs are aligned with one another along a longitudinal axis of alignment.
 6. The three phase output AC bus bar sub-assembly according to claim 1, wherein the output tab of each of the three bus bars is disposed on a lower end of the bar body and the plurality of power modules are disposed on an upper end of the bar body.
 7. The three phase output AC bus bar sub-assembly according to claim 1, wherein the output tab of the second of the three bus bars has a substantially serpentine shaped section that allows the output tab of the first of the three bus bars and the output tab of the third of the three bus bars to be spaced equidistantly from the output tab of the second of the three bus bars when the three bus bars are placed into mating relationship with one another.
 8. The three phase output AC bus bar sub-assembly according to claim 1, wherein the second of the three bus bars is laterally offset from the first of the three bus bars and the third of the three bus bars is laterally offset from the second of the three bus bars.
 9. The three phase output AC bus bar sub-assembly according to claim 1, wherein each of the three bus bars is configured to carry a unique phase of an AC power signal generated by the plurality of power modules.
 10. A three phase output AC bus bar sub-assembly for an inverter assembly, the three phase output AC bus bar sub-assembly comprising: three bus bars each comprising: a bar body having a front surface and a back surface, wherein the front surface and the back surface both comprise an insulating coating; a plurality of power module tabs spaced apart from one another so as to allow a first of the plurality of power module tabs to couple with a first power module of the inverter assembly and a second of the plurality of power module tabs to couple with a second power module of the inverter assembly, the plurality of power module tabs extending away from the back surface; and an output tab extending from the front surface; and the bar body of a first of the three bus bars is positioned behind the bar body of a second of the three bus bars and a third of the three bus bars is positioned in front of the second of the three bus bars.
 11. The three phase output AC bus bar sub-assembly according to claim 10, wherein one of the plurality of power module tabs of a second of the three bus bars is disposed in between the plurality of power module tabs of a first of the three bus bars.
 12. The three phase output AC bus bar sub-assembly according to claim 11, wherein one of the plurality of power module tabs of a third of the three bus bars is disposed in between the plurality of power module tabs of the first of the three bus bars and the second of the three bus bars.
 13. The three phase output AC bus bar sub-assembly according to claim 10, wherein the plurality of power module tabs extend in linear alignment with one another and are coplanar.
 14. The three phase output AC bus bar sub-assembly according to claim 10, wherein the output tabs of the three bus bars extend in linear alignment with one another and are coplanar.
 15. The three phase output AC bus bar sub-assembly according to claim 10, wherein a length of the plurality of power module tabs of a third of the three bus bars is greater than a length of the plurality of power module tabs of a second of the three bus bars, and a length of the plurality of power module tabs of the second of the three bus bars is greater than a length of the plurality of power module tabs of a first of the three bus bars.
 16. The three phase output AC bus bar sub-assembly according to claim 10, wherein a first of the three bus bars is in a rearmost position, a second of the three bus bars is in a middle position, and a third of the three bus bars is in a foremost position.
 17. The three phase output AC bus bar sub-assembly according to claim 16, wherein the output bar of the first of the three bus bars extends under the bar body of the second of the three bus bars and the output bar of the second of the three bus bars extends under the bar body of the third of the three bus bars.
 18. The three phase output AC bus bar sub-assembly according to claim 16, wherein one of the plurality of power module tabs of the second of the three bus bars overlaps the bar body of the first of the three bus bars, further wherein one of the plurality of power module tabs of the third of the three bus bars overlaps the bar body of the first of the three bus bars and the bar body of the second of the three bus bars.
 19. A three phase output AC bus bar sub-assembly, comprising: an offset arrangement of three bus bars, the three bus bars each comprising: a pair of power module tabs extending perpendicularly from a bar body, the pair of power module tabs disposed on opposing sides of the bar body; and an output bar extending perpendicularly from the bar body in a direction that is opposite of a direction of the pair of power module tabs, wherein the output bar is disposed between the pair of power module tabs; and a mounting plate that receives the output bars of the three bus bars; and wherein the pair of power module tabs of the three bus bars extend in linear alignment with one another along a line of symmetry.
 20. The three phase output AC bus bar sub-assembly according to claim 19, wherein the mounting plate is substrate that is disposed in parallel to the bar body of a foremost of the three bus bars. 